1. M D1 S1 D2 S2 D3 S3 D4 S4 D5 S5 D6 S6 D7 S7 D8 S8 D9 S9 250 150 75 100 50 37 25 20 15 10 Supplemental Figure 1. A typical titration curve (peptide VANYVDWINDR) shows the correct amount of heavy peptide needed to be spiked-in to human blood samples (100 femtomole in this case). X-axis: peptide amount in femtomole, y-axis: total peak AUC (area under transition curve). Synthetic heavy-labeled peptide is in red and endogenous light peptide is in blue.

2. Supplemental Figure 2. A typical titration curve (peptide VANYVDWINDR) shows the correct amount of heavy peptide needed to be spiked-in to human blood samples (100 femtomole in this case). X-axis: peptide amount in femtomole, y-axis: total AUC (area under transition curve). Synthetic heavy-labeled peptide is in red and endogenous light peptide is in blue.

3. A1BG/SGLSTGWTQLSK light heavy light heavy CFH/CTSTGWIPAPR lightheavy RBP4/YWGVASFLQK light heavy IGFALS/VAGLLEDTFPGLLGLR PROC/TFVLNFIK light heavy Supplementary Figure 3. Typical chromatograms of 5 targeted peptides.

4. PROC RBP4 Supplemental Figure 4. The mean of serum protein levels among control, Ishak 2-4 and Ishak 5-6 patient samples. There is a significant decrease of PROC levels in Ishak 5-6 patients as compared to Ishak 2-4 patients (P=0.004). PROC levels in Ishak 5-6 patients are also significantly lower than controls (P=0.00005). Both Ishak 2-4 and patients 5-6 patients’ RBP4 levels are significantly lower than controls (P=0.01 and P=0.0001 with or without outliers, respectively). Comparison of RBP4 levels in Ishak 5-6 patients to Ishak 2-4 patients shows a P value of 0.07 with outliers and P value of 0.02 without outliers.